Of course, no one should invest with non-discretionary income since that would be gambling rather than investing, and yeah, discretionary income can be increased by increasing income and/or decreasing expenses.
Yeah it would seem more like gambling if one goes beyond discretionary income but some times I do have this feeling if we are only buying bitcoin with an amount can afford to loss them doesn't that make it a gambling because we are afraid we might losses them? lossing can be in many ways but the most fear in this instance is the fear of lossing it to crash or hacks/attacks. I prefer to invest into bitcoin with an amount that I can afford but not the chunks from my discretionary income, if we keep it being only a little of what we can afford to loss to me it's now a gamble which bitcoin is not.
Going beyond using our discretional income to accumulate bitcoin might gives us difficulties in maintaining and sustaining our bitcoin investment for the long term. As potential investors in Bitcoin,We cannot use cash meant for our personal needs to invest in Bitcoin,it is important we sort out basic needs first from our available funds and whatever is left should be used to buy Bitcoin periodically. Using our discretional income keeps us consistent in accumulating Bitcoin not minding the risks. Sometimes an investor might decide to go aggressive in accumulating Bitcoin but should be doing so within his financial capability and shouldn't go beyond what he can afford to do way because he wants to be aggressive in building his portfolio.
Wish you had a good knowledge of this forum and it's wall observers you would have figured out that investing in bitcoin years back was not on discretionary income, there is a popular meme that guys go all in in bitcoin which I'm very partially sure JayJuanGee would be able to remember that guys who were actively investing back then even sold some important stuffs just to invest, we have memes flying around that guys leaved in an empty apartment just few stuffs and his laptop and bitcoin that's all, but guess what after four years of this pain or management, or 8 years of management he is now able to afford everything and still have his investment yet still stacking up, the problem most of you guys in this thread have is that you refused to explore, learn and see things for yourselves but only depends on a few words flying around. you have to take what you want to take you somewhere serious bitcoin is that one thing you can take that seriously and come back 8 years to a top achievement.